Overload Operator Recieving Segment Fault

oonej (208)
I have a function that checks for a specific parameter, if that parameter is incorrect i need it to send a null pointer or something to an overloaded ostream operator.

within the ostream operator it will check for this null pointer and print an error message otherwise it will print the normal desired results..

my problem lies when I try to run this on a unix based system and i get a "Segmentation Fault" error message and it aborts the program.

What way would you go around this?

My function to check for error
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Matrix Matrix::operator*(const Matrix& test)
    {
           
           if(  test.num_cols() == this->num_rows()) {  
            
                
               Matrix tmp(num_rows(), test.num_cols());
               for(int i = 0; i < num_rows(); i++){
                   for(int j = 0; j < test.num_cols(); j++){
                       for(int l = 0; l < num_cols(); l++){
                                   tmp.mydata[i][j] += this->mydata[i][l] * test.mydata[l][j];
                       }
                   }
               }
                
               return tmp;
            } 
            else {
                 return *this; //need this to return a null pointer.. its *this to avoid the seg error
                 //Matrix *ptr = NULL;
                 
                 //return *ptr;
                 
                 }
          
    }


ostream overloaded
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ostream& operator << (ostream& os, const Matrix& test) {
            if(test == NULL){
                os << "Error";

            } 
            else
            {       
             for(int i = 0; i < test.num_rows(); i++){
               for(int j = 0; j < test.num_cols(); j++){
                       os << setw(6) << test.get_element(i, j) << " ";           
               }
               os << "\n";
           }  
           os << endl;  
          }
  return os;    
}
cire (8284)
You were definitely playing with fire there.

I would suggest throwing an exception.
oonej (208)
how do i throw an exception to the ostream? there is pretty poor documentation, at least for my understanding on try/catch/throw methodology
therockon7throw (284)
Hi

Either do it by using assert( test.num_cols() == this->num_rows() );, or excetiopn
If you still dont want to use niether of them, than 


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Matrix Matrix::operator*(const Matrix& test)
    {
           Matrix tmp;// default constructor must set col and row-sizes = 0
                            // and allocate  no memory
           if(  test.num_cols() == this->num_rows()) {             
                
              tmp.resize(num_rows(), test.num_cols()); // resize must be availble
               for(int i = 0; i < num_rows(); i++){
                   for(int j = 0; j < test.num_cols(); j++){
                       for(int l = 0; l < num_cols(); l++){
                                   tmp.mydata[i][j] += this->mydata[i][l] * test.mydata[l][j];
                       }
                   }
               }
                
               
            } 
           return tmp;
          
    }


and 

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ostream& operator << (ostream& os, const Matrix& test) {
            if(test ==0){ // you must overload operator==(int ), or do the folllowing check
            //if( test.num_rows() == 0 || test.num_cols() == 0 ){
                os << "Error";

            } 
            else
            {       
             for(int i = 0; i < test.num_rows(); i++){
               for(int j = 0; j < test.num_cols(); j++){
                       os << setw(6) << test.get_element(i, j) << " ";           
               }
               os << "\n";
           }  
           os << endl;  
          }
  return os;    
}



Last edited on
oonej (208)
Thanks, didn't even think of doing it that way :)

good call
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